Day 2 (11/7) Flashcards
What is a hominin
Anything after the split between humans and chimps/bonobos
What came first, bipedalism or large brain size?
bipedalism
Describe the trend of how teeth changed in hominins
canines morphed from being big/ sexual selection for fighting to smaller
Describe the trend in aborealism with the evolution of hominins
More frequent (chimps) to less common
Sahelanthropus tchadensis location
Chad, Africa
Sahelanthropus tchadensis age
7-6 MYA
Is Sahelanthropus tchadensis bipedal or not
yes, bipedal
Sahelanthropus tchadensis brain size
360cc
Sahelanthropus tchadensis brow ridge
huge brow ridge
Sahelanthropus tchadensis canines
small (already trend)
How is the presence of bipedalism determined from fossils?
location of spinal column emerging from skull (foramen magnum)
Orrorin tugenensis location
Kenya, Africa
Orrorin tugenensis age
6.1-5.8 mya
Orrorin tugenensis femur as proof of bipedalism
there was great gravitational force on the inside of the top of the femur, making the bone thicker there
What is one common approach for interpreting function from fossils?
biomechanics
Wolff’s Law
bone growth in response to mechanical stress
Ardipithecus kadabba location
Ethiopia, Africa
Ardipithecus kadabba age
5.8 - 5.2 mya
Ardipithecus kadabba bipedal?
yes, Ardipithecus kadabba bipedal
Ardipithecus kadabba canines?
Ape-like; small, but pointy
Space between teeth that allows canines to connect) ?
Ardipithecus ramidus location
Ethiopia, Africa
Ardipithecus ramidus age
4.4 mya
Ardipithecus ramidus skull overall
ape-like (smaller)
Ardipithecus ramidus prognathism
Similar to chimps, bottom half of face juts out. “primitive/ancestral trait”
Ardipithecus ramidus brain size
small, 325cc, smaller than some chimps
Ardipithecus ramidus canines
chimp-like, but a bit smaller
Ardipithecus ramidus molars
??? suggest a broader diet than chimps
Ardipithecus ramidus locomotion
long arms and curved fingers suggests climbing and tree use, but not a knucklewalker (this is generally true of Ardipithecus species)
human hip bones compared to Ardipithecus ramidus
humans have much taller hip bones with a wider flat area
human ilium compared to Ardipithecus ramidus
similar, wide and low
What is the ilium
blade of the pelvis
What is significant about the ischium
where the hamstring muscle attaches
Ardipithecus ramidus ischium
chimp-like. an adaptation for vertical climbing
Ardipithecus ramidus feet
ape-like, divergent big toe
Name the two theories for why bipedalism developed
Arboreal theory and Savannah theory
Describe the arboreal theory for bipedalism
Because hominins existed in the trees, there is something more efficient about being bipedal in the trees (reaching and stability)
Describe the savannah theory for bipedalism
as the climate is cooling (hot and wet vs. cold and dry), resources are more patchily distributed. Theory seems unlikely because- earliest hominins found in forests not savannas and bipedalism is not more efficient
Australopithecus anamensis location
Ethiopia, Africa
Australopithecus anamensis age
4.2 - 3.9 mya
Australopithecus anamensis bipedal?
yes
did Australopithecus anamensis have sagittal crest?
yes
Australopithecus anamensis canines
small
Australopithecus anamensis brain size
370cc
Australopithecus anamensis tibia
top is wider (like gorillas)
Was the transition from Australopithecus anamensis to Australopithecus afarensis anagenesis or cladogenesis?
Skull discovery supports cladogenesis because the daughter species not a general transition from one to the other
